APPENDIX C

AGRICULTURE

The agricultural system is derived from standard nutritional
requirements for adult men and women and for children. The space colony
population is used to normalize these requirements to that of a "typical"
person weighing 60 kg as shown in table 5-16.

TABLE 5-16.- HUMAN NUTRITIONAL REQUIREMENTS

*Colony workers may require higher protein intake due to
strenuous workloads.
**Assumes a normal age and sex distribution of children under
18 years old.

These requirements are met by
an average daily diet which is shown in table 5-17 (a) which also includes
the caloric and nutritional values calculated for this diet. The
nutritional requirements are met and an excess of protein is provided by
a substantial margin.

A more careful analysis of
the colony's protein requirement could provide savings in meat
requirements and, in turn, provide substantial savings in the required
land area for plants.

The diet is treated as a daily average of all components as if each
colonist ate a small portion of each foodstuff each day. In reality, of
course, the colonists would eat a varied selection that over time
averages to this diet. The individual components of the diet are chosen
to provide adequate variety for both-nutritional and psychological
purposes. These components are meant to be representative of classes of
foods and not specifically limited to these items. For example, pork
could be considered as a feasible diet component with feed and area
requirements intermediate between beef and rabbits. In addition, it
should be explicitly stated that this diet represents typical American
preferences and does not recognize ethnic or religious dietary
preferences. It is reasonable to expect, however, that such preferences
could be adopted if desired.

The meat in this diet dictates the requirement for a stable herd of
animals for which the rates of birth and slaughter are equal. In effect,
each colonist has 26 fish, 6.2 chickens, 2.8 rabbits and about 1/7 of a
cow (see table 5-5). The plant diet for these animals plus that for
humans then forms a total requirement for all plants as given in
table
5-18.

Food processing byproducts and silage are extensively used in
satisfying the animal diet. Implicit in this derivation is allowance for
yields in meat dressing and food processing, for moisture and silage
content of the grains, and for the metabolic requirements of the various
animals. These factors are given in table 5-19, parts A-J, along with the
carbon, nitrogen, hydrogen, and oxygen elemental balance for each step in
the food chain (refer to fig. 5-16).

TABLE 5-19.- J

Mass balance waste processing

Total

C

H

O

N

(In) WastesO2

62,0602,476

862-

6759-

54,3672,476

72-

(Out) CO2NH4
H2O

3,1939361,250

862--

-216738

2,331-54,512

-72-

Sorghum is chosen as a principal
component of the animal diet because it can be produced in excellent
yield and because it provides a source of protein (11 percent) while also
providing silage and sugar. Protein make-up for the animal diet is
provided from soybean (34 percent) and from meat processing byproducts.

From the quantitative requirements for each plant component, total plant
growing area requirements can be obtained based upon estimates of crop
yields as presented in table 5-4.

The success of the colony's agricultural systems rests entirely upon the
photosynthetic productivity. Crops were estimated assuming a yield double
that of the world record for that crop, as shown in table 5-20.

In addition, a factor of 1.1 improvement is obtained by shortening the
growing season from 100 to 90 days. The record yield data come from
harvests under good but not ideal or controlled growing conditions.
Comparison of typical terrestrial and space colony growing conditions is
presented in table 5-21.

Including the shortened season, the net
improvement is a factor of 2.2 which is further enhanced by harvesting 4
crops per year. Thus the farmer in a typical American Midwestern farm who
produces 100 bushels of corn per acre in a single season year would look
with astonishment on the space colony farmer who produces 4164 bushels of
corn from a single acre in his 4-season year. While this factor of 40 is
substantial, it is believed to be credible since a portion of it is
derived from year-round growing. Substantiation of crop yields is
required and can be obtained through careful study under controlled
conditions (and most of the research could be performed on Earth). The
improvement that has already been achieved for certain vegetables in Abu
Dhabi (ref. 5) is shown in
table 5-22.

The summer study did not pursue the issue of food reserves, design
margins and safety factors with respect to agriculture. Due to the
importance and fragility of the agricultural system further study should consider this issue. In general,
it was felt desirable to produce some excess food continuously, store
some of the excess as reserve, and recycle the remainder. In fact, it
would seem wise to design the system such that the colony could survive
on the output of two of the three agricultural units for a period of
several months if some disaster ruined production in one of the areas.
Also, the study did not pursue microbial and insect ecology but did
assume that these important areas could be resolved upon further study.